West Nile Virus ID’d in mosquito trapped in Plainville

A mosquito collected from a trap in Plainville has tested positive for West Nile Virus, the Board of Health announced today, but there have been no reports of human infection.

Heather McCarron/STAFF WRITER

A mosquito collected from a trap in Plainville has tested positive for West Nile Virus, the Board of Health announced today, but there have been no reports of human infection.

The mosquito was trapped on the south side of town on Sept. 26. Board of Health administrative assistant Debbie Revelle said the board just got the call today on the findings for the mosquito — the first specimen collected in Plainville this year to test positive for the disease.

“It’s important to note the species is primarily a bird biter,” said Revelle, but noted that on occasion the mosquito may bite humans and other mammals.

The mosquito species is Culiseta melanura. A specimen collected in Sharon also tested positive, according to John Smith of the Norfolk County Mosquito Control Project, noting West Nile Virus and Eastern Equine Encephalitis have both been identified in the area.

With temperatures predicted to fall this week, Smith said there are no plans to spray.

“What we suggest is people take the normal precautions they would if they are in mosquito areas,” he said.

Once the first hard frost hits, he said, mosquitoes will no longer be an issue. Until then, “we really can’t completely drop our guard,” he said.

Concern about potential human infection would be elevated, Smith said, “if, number one, it was EEE (Eastern Equine Encephalitis) and, number two, it (the mosquito) was in a human-biting species.”

According to the Massachusetts Department of Public Health (DPH) there have been three cases of West Nile Virus infection in Massachusetts residents this year, the most recent one in September — that patient, a resident of an unidentified Norfolk County town, was hospitalized for eight days, but has recovered and been discharged. Seven human cases of West Nile Virus were identified last year.

West Nile Virus is most commonly transmitted to humans by the bite of a mosquito infected with the virus. While West Nile can infect people of all ages, people over the age of 50 are at higher risk for severe disease, according to the DPH.

Most people infected with West Nile will have no symptoms; about 20 percent will develop a fever, head and body aches, nausea, vomiting and sometimes swollen lymph glands. Some people may laos develop a skin rash on the chest, stomach and back. Less than 1 percent of people infected with West Nile develop more severe illness, including encephalitis or meningitis.

“Sometimes it’s hard to believe that mosquito bites, particularly in the fall, are anything other than a minor annoyance,” said Dr. Al DeMaria, state epidemiologist. “We tell people about these infections to remind them that there can be serious consequences to mosquito bites, even in the fall; but there are steps people can take to protect themselves and their loved ones … use mosquito repellent and clothing and move indoors if you have to; just don’t get bitten.”

Revelle said the health board issued a previous advisory letting people know West Nile and EEE are in the area and “just to take precautions and do what you need to do.” Recently, EEE was identified in a mosquito trapped in Medway. There has been one confirmed case of EEE in a Massachusetts resident this year; EEE is a serious disease in all ages and can even cause death.

“Hopefully it won’t be too long before we get a hard frost and we won’t have to deal with this anymore,” Revelle said.

The health board's advisory issued today notes that, "by taking a few, common-sense precautions, people can help to protect themselves and their loved ones."

First and foremost, avoid mosquito bites by being aware of peak mosquito hours.

“The hours from dusk to dawn are peak biting times for many mosquitoes. Consider rescheduling outdoor activities that occur during evening or early morning. Otherwise, take extra care to use repellent and protective clothing,” the health board advises.

Clothing can also help reduce mosquito bites. “Although it may be difficult to do when it’s hot, wearing long-sleeves, long pants and socks when outdoors will help keep mosquitoes away from your skin,” the health board advisory reads.

People are advised to apply insect repellent when outdoors as well. Use a repellent with DEET (N, N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), IR3535 or oil of lemon eucalyptus [p-methane 3, 8-diol (PMD)].

DEET products should not be used on infants under two months of age and should be used in concentrations of 30 percent or less on older children. Oil of lemon eucalyptus should not be used on children under three years of age. Permethrin products are intended for use on items such as clothing, shoes, bed nets and camping gear and should not be applied to skin.

Other tips:

Drain standing water, since mosquitoes lay their eggs in standing water. Limit the number of places around your home for mosquitoes to breed by either draining or getting rid of items that hold water. Check rain gutters and drains. Empty any unused flowerpots and wading pools, and change water in birdbaths frequently.

Install or repair screens, since some mosquitoes like to come indoors. Keep them outside by having tightly-fitting screens on all of your windows and doors.

Information about WNV and reports of WNV activity in Massachusetts can be found on the MDPH website at http://www.mass.gov/dph/wnv.

Information is also available from the Norfolk County Mosquito Control Project’s website at www.massnrc.org/ncmcp/.

Recorded information about WNV is also available by calling the MDPH Public Health Information Line at 1-866-MASS-WNV (1-866-627-7968).